Any fixed orthodontic appliance consists of a plurality of brackets, molar tubes, arch wires, and orthodontic auxiliaries. One bracket or one molar tube is needed for an individual tooth for engaging the arch wires. A bracket is a block having a contoured surface called a base, matching with the tooth contour and a body having slots for engaging arch wires, lock-pins, ligature wires, and hooks for engaging elastics.
The brackets are attached to the central and the lateral incisors, the canines and the first and the second premolars in the upper and the lower dental arches by means of metal bands or are directly bonded with adhesives.
A molar attachment is a block having a base matching with the tooth contour and one or more round and/or rectangular tubes. The molar attachment is usually referred to as a molar tube. The molar tubes are attached to the first and the second molars in the upper and the lower dental arches by means of metal bands or are directly bonded to the teeth with adhesives.
Various types of arch wires are used which pass through the molar tubes and the arch wire slots in the brackets. The arch wires and various types of elastics engaged to the hooks on the brackets, the molar tubes, and the arch wires exert pressure which move the teeth in the jaw bones for correcting their irregularities.
The conventional fixed appliances can be categorized as
i. The Edgewise Appliance and its modifications, mainly the Straight Wire Appliance and the Tip-Edge Appliance; PA1 ii. The Begg Appliance; and PA1 iii. The combination appliances. PA1 1. The brackets have horizontal slots which do not allow free tipping of the teeth in clockwise and anticlockwise directions during retraction of the teeth; PA1 2. The teeth move bodily which requires heavy forces causing severe discomfort and pain to the patient; and PA1 3. The anchorage has to be reinforced by means of a headgear requiring more cooperation from the patient. Moreover the headgear can cause soft tissue injuries. PA1 1. The bracket does not allow the tooth to tip more if needed; PA1 2. Uprighting springs are needed and sometimes even torquing springs are also needed; and PA1 3. It comprises of a bracket which allows limited tipping of teeth in one direction only. PA1 1. Since the bracket is narrow and has a slot in the gingival surface it allows uncontrolled tipping of the teeth and the rotation control is inadequate; PA1 2. The tooth movements are not self-limiting; PA1 3. Since the diameter of the molar tube is much larger than that of the arch wire used there is a tendency for the arch wire to roll in the tube resulting in an inadequate molar control and loss of anchorage; PA1 4. The positioning of the teeth is not as precise as that obtained with rectangular arch wires because rectangular arch wires are not used with the Begg Appliance; PA1 5. It requires uprighting and torquing auxiliaries for positioning of the roots taking up a considerable chairside time since additional wire bending is needed; PA1 6. Due to the particular design of the brackets and the molar tubes of the Begg Appliance, there is a tendency for the upper molars to flare distobuccally during the last stage of the treatment procedure when torquing and uprighting springs are placed for the final settlement of the teeth; and PA1 7. It is difficult to move the posterior teeth mesially as the anterior teeth cannot provide adequate anchorage due to the bracket design. PA1 1. The brackets are bulky; PA1 2. Tipping cannot be controlled as with the Begg Appliance; and PA1 3. Uprighting springs have to be used. PA1 1. To allow rapid, differential movements of the teeth with better control and less friction using light tipping forces; PA1 2. To allow free tipping, controlled tipping or bodily movement of the teeth in any plane of space as desired by the orthodontist; PA1 3. To provide better anchorage control by allowing tipping of a single tooth or a group of teeth and by bodily movement of the anchor teeth as tipping requires much less force than bodily movement; PA1 4. To allow proper setting of the teeth with three dimensional control over all the teeth using a rectangular arch wire; PA1 5. To allow effective and rapid opening of the bite; PA1 6. To eliminate the use of heavy forces which cause discomfort and pain to the patient; PA1 7. To reduce the need for patient cooperation; PA1 8. To provide facility for the use of a headgear to apply orthopedic forces to the upper jaw to correct jaw discrepancies in a growing patient; PA1 9. To allow better control over the anchor molars; PA1 10. to reduce the chair side time needed by the orthodontist; and PA1 11. to reduce the duration of the treatment.
In the existing Edgewise Appliance the bracket has a single horizontal rectangular slot on the labial/buccal surface or the face of the bracket for engaging arch wires and the molar tube is horizontal, and rectangular in cross-section. Normally two tubes, one rectangular and one round for a headgear, are used for the first molars in the Edgewise Appliance. The headgear is used for an additional anchorage by means of an extraoral force or for orthopedic correction of the jaw bones. It consists of a facebow and a head or neck strap. The inner bow of the facebow fits into the round tube.
The arch wires have to be bent precisely in all three planes of space to set the teeth in the desired positions. This takes up a lot of clinical time of the orthodontist and so the brackets and the molar tubes were modified.
The Straight Wire Appliance is a modification of the Edgewise Appliance which comprises of preadjusted brackets and molar tubes. The horizontal slot in the face of the bracket is placed at an angle with the base of the bracket called the torque angle. The horizontal slot is also placed at an angle with the long axis of the tooth called the tip angle. The thickness of the base of the bracket varies for an individual tooth. The molar tube is also angulated in the vertical as well as in the horizontal directions. All these modifications minimize the need for bends in the arch wires to place the teeth in their ideal positions. The tip angle, the torque angle, and the thickness of the base of each of the brackets vary as the shapes, sizes, and inclinations of the teeth are different.
The Edgewise Appliance and its modifications have the following disadvantages:
The Tip-Edge bracket is another modification of the edgewise bracket. (U.S. Pat. No. 5,125,832). The bracket used in Tip-Edge Appliance has a vertical slot through the body of the bracket for uprighting springs and a rectangular horizontal slot in the face of the bracket for engaging arch wires. The horizontal arch wire slot of the bracket is cut in such a manner that it allows limited tipping of the tooth in one direction only. The molar tube is horizontal, and rectangular in cross-section such that the width is more than the height.
The disadvantages of the Tip-Edge Appliance are:
The bracket used in the Begg Appliance has a horizontal slot in the gingival surface of the bracket for the arch wires, a vertical slot through the body of the bracket for lock-pins, uprighting springs, and derotating springs, and a base conforming to the contour of the tooth surface. The molar tube used in the Begg Appliance is horizontal, and round in cross-section. Only round arch wires are used with the Begg Appliance during the treatment. The teeth are positioned in their desired places with the help of the main arch wires and auxiliary springs.
The disadvantages of the Begg Appliance are as follows:
The combination appliances were developed to eliminate the drawbacks of the Edgewise, the modified Edgewise and the Begg Appliances.
The brackets used in the Combined Anchorage Technique (CAT) and other combination appliances (U.S. Pat. Nos. 5,037,297; 4,496,318; 4,427,381; 3,163,933) have two rectangular slots for the arch wires, one horizontal in the gingival surface of the bracket and the other horizontal in the face of the bracket. One vertical slot through the body is used for uprighting springs, and for lock-pins and ligature wires which secure the arch wire to the horizontal arch wire slot in the gingival surface as in the Begg Appliance. The arch wires used are round for the initial tooth movements and are engaged to the horizontal slots in the gingival surface of the brackets. The precise positioning of the teeth is brought about by rectangular arch wires engaged to the rectangular slots as in the Edgewise Appliance and its modifications.
The disadvantages of the combination appliances are: